Secondarily added elevator structure

The invention relates to a secondarily added elevator structure, which comprises a multi-layer building, a parallel double stair, an elevator device and a channel, wherein the channel is connected with the elevator device and the multi-layer building; the parallel double stair comprises a first stair segment and a second stair segment for connecting floors and a middle platform for connecting the first stair segment and the second stair segment; the elevator device comprises an elevator shaft and an elevator car moving in the elevator shaft; the channel comprises a cell door hole arranged on a stair outer wall at the side of the middle platform, an elevator waiting car and a landing door; the elevator waiting car and the middle platform are arranged at the same height, the elevator waiting car is arranged between the elevator shaft and the stair outer wall; the landing door is arranged on a first shaft well of the elevator shaft; the elevator shaft is arranged next to the stair outer wall and oppositely to th